Welcome to Northern Ireland, where MOT & tax reminders are both issued as a courtesy by DVANI, although they occasionally miss one (our MOTs are still government run - long story, lost in the mists of time).
Once you have your tax and MOT discs, they must (by law) be displayed on the vehicle - LHS of car winscreen, or LHS of bike, although I've never heard of anyone being prosecuted for non-display. Having them clearly visible also acts as a visual reminder for me, as 3x bikes + 2x cars = 10x dates to remember (yes, my wife reckons its MY fault if her car's tax or MOT expires...).
The MOT disc comes on an A5 paper certificate, which you send off with your tax application and insurance certificate, and the fee. It still irks me that I pay more to tax each of my bikes than my mum pays for her (low emissions) car - and that 2 of my bikes can only be taxed for 12 months (not 6) because they are under 600cc! The admin charge for cancellation means that it isn't really worthwhile - sounds like the government is profiteering...okay, so sue me for treason!
That said, keeping my 3x bikes taxed, tested, and insured still only costs about the same as my wife's annual gym membership...and I think I get a better return on the investment - although mine is more psychological than physical.
Joe